The purpose of the invention is to decrease the recycling cost of refractory metal products, and, in particular, to rejuvenate sputtering targets having backing plate structures attached.
Sputtering targets of high temperature materials, such as tantalum and other refractory metals used in integrated circuit manufacture and other electrical, magnetic and optical product manufacture usually are eroded in a non-uniform way during the process of sputtering which leads to a race track like trench on the operating side of the target. In order to prevent any contamination of the substrates or catastrophic break-through of coolant fluids behind the target, the targets generally are withdrawn from service well before the refractory sputter metal is penetrated, accepting the need for a new target after only a minor portion (typically from 25 to 35% of the target depending on the target design) of the sputter metal has been consumed. The major part of the sputter target can be resold only at scrap price or recycled with difficulty. In addition, the backing plate of the target must be removed and may be re-bonded to a new sputter metal plate for recycling.
Published German application 19,925,330 suggests a process for recycling sputtering targets wherein the target material is poured in pieces or as liquefied material to the consumed portions of the target. Thereafter, thermal energy (provided via infrared radiation) is introduced in the direction of the target. The target material is completely melted and allowed to solidify. Finally, published European patent application 834,594 suggests that sputtering targets can be recycled after use by adding a refractory metal powder to the consumed portions of the target and pressing the powder under heat and pressure.
It is a principal object of the invention to replace current recycling processes by the rejuvenation of the refractory metal product (preferably a sputtering target). It is also an object of the invention to improve the cost and speed of getting used sputtering targets back into service. Finally, it is a further object of the invention to establish a microstructure of the fill zone at least as good as on the balance of the target.